1. Field of the Invention
The present invention relates to a display device, and more particularly to a laminated liquid crystal display device.
2. Description of the Related Art
A laminated liquid crystal display device, in which substrates such as liquid crystal substrates are laminated, is known as a liquid crystal display device. There are several types of laminated liquid crystal display device of this type. Among them are a display device that has a touch input panel laminated on the front of a display panel formed by a liquid crystal substrate and a display device that has two laminated display panels.
FIG. 11 is a diagram showing an example of one configuration of a laminated liquid crystal display device that is conventionally known. In the example of the configuration shown in FIG. 11, first liquid crystal cell panel 110 and second liquid crystal cell panel 120 are laminated. The first liquid crystal cell panel 110 has a configuration in which a liquid crystal layer 112 is held between a first panel substrate 111 and a first opposed substrate 113. The second liquid crystal cell panel 120 has the similar configuration in which a liquid crystal layer 122 is held between a second panel substrate 121 and a second opposed substrate 123. An electrode 114 is provided on the first panel substrate 111, an electrode 124 is provided on the second panel substrate 121. Those electrodes are provided to supply the liquid crystal panel a driving signal or to output a signal detected on the touch panel.
The liquid crystal display device is one display assembly composed of the first liquid crystal cell panel 110 and the second liquid crystal cell panel 120. Normally, the driving signal is supplied to, and a detected signal is output from, this display assembly via one wire line. In some cases, the first liquid crystal cell panel 110 and the second liquid crystal cell panel 120 are driven in synchronization with each other.
To satisfy the requirements described above, the liquid crystal display device has one wire line (FPC 140 in FIG. 11) via which input/output is performed with an external device and, within the liquid crystal display device, signals are branched between the first liquid crystal cell panel 110 and the second liquid crystal cell panel 120. Because the first liquid crystal cell panel 110 and the second liquid crystal cell panel 120 are laminated, the first panel substrate 111 and the second panel substrate 121, which are separated, must be connected electrically.
Conventionally, a configuration is known in which a conductive element 130, such as an anisotropic conductive element, is provided between the first panel substrate 111 and the second panel substrate 121 to electrically connect between those panel substrates.
In the laminated configuration in which two panels are provided on both sides of an intermediate substrate with this intermediate substrate as the common substrate, another configuration is proposed in which the two panels are configured by bending one film substrate in order to establish an electrical connection between the two panels (for example, see Patent Document 1).
[Patent Document 1] Japanese Patent Laid-Open Publication No. 2001-154178
In the configuration described above in which the conductive element 130 is held between the first panel substrate 111 and the second panel substrate 121 to electrically connect between both panel substrates, it is desired that this conductive element 130 be electrically connected properly to the first panel substrate 111 and the second panel substrate 121. To satisfy this requirement, the first panel substrate 111 and the second panel substrate 121 are rigid enough to press the conductive element 130 on the panel substrates.
On the other hand, when the panel substrate of one of the liquid crystal cell panels is made of a flexible material such as plastic, the panel substrate is not rigid enough for the panel substrate alone to press the conductive element 130 on the panel substrate. In this case, there is a possibility that the electrical contact is insufficient. To press the conductive element on the panel substrate properly, a press structure such as an enclosure for enclosing the liquid crystal cell panel must be provided separately.
One of the problems with the configuration described in Patent Document 1 given above is that, though there is no need for a conductive element for electrically connecting the two panel substrates, the electrodes for each liquid crystal panel must be formed on both faces (rear face and front face) of the intermediate substrate shared by both panel substrates. Another problem is that the formation process of the liquid crystal panel becomes complicated because liquid crystal must be injected into the empty cell panels formed on both faces on the intermediate substrate.